Then give a few of the top ones.
1. Her ego. She was passed over for VP (without even the courtesy of a vetting) after having been the front-runner in the campaign.
2. Calculus. She runs now with Obama, she'll go down to defeat and become radioactive for a 2012 consideration.
3. Timing. If she simply waits four years, she'll have built her credentials and supporter base substantially by 2012.
4. Addition. She brings nothing substantially different to the ticket, ideologically.
5. Me Too! Adding Hillary to the ticket would simply appear as sexist pandering, and following the Republican's lead. They will not willingly choose to look inferior to the voters.
That enough for ya?